This project is designed to determine the genetic basis of peptide hormone-surface receptor interactions, the genetic variations in the regulatory receptor molecules, and the type of metabolic alterations to be expected from mutations involving hormone function. Two antagonistic peptide hormones, insulin and glucagon, and their receptor-mediated hormonal signal transfer systems will be studied by somatic cell genetic approaches in combination with biochemical and immunological techniques. These hormones play important roles in diabetes and obesity. The genetic analysis will allow the identification of the genes responsible for production and regulation of human surface receptors for the peptide hormones and the assignment of the genes to specific human chromosomes. A series of insulin (or glucagon)-nonresponsive clones will be selected from in vitro mutagenized human mouse somatic cells and from diabetic and obese human and mouse related to hormone resistance. It is expected that various states of receptor-deficiency will be found: some mutants will owe their unresponsive phenotype to mutations in structural genes for receptor molecules and others may be due to mutations in regulatory genes responsible for hormonal signal transfer. The biochemical and genetic nature of receptor-negative and deficient state and their effects on corresponding metabolic pathways will be studied. The receptor-negative mutants of mouse origin will be fused with microcells derived from human wild type cells which express human receptors and the resulting human x mouse cell hybrids will be analyzed with regard to species origin of the expressed receptors and the constitution of chromosomes and genetic markers. Segregation analysis of these parameters in a series of human x mouse somatic cell hybrids will permit mapping of the human genes responsible for production of functional receptors and/or the genes capable of regulating the enzymes involved in hormone-mediated metabolic pathways. The proposed study is also designed to dissect human cell surface components genetically using specific antisera.